1. Field of the Invention
The present invention relates to a container closure system with an inner seal in a cap. The inner seal of the present invention is useful for use in closures of a wide range of sizes and types of containers in glass, plastics, metal and paper.
2. Description of the Prior Art
Various attempts have been made to prevent contamination and deterioration of contents in containers. For example, house instant coffee, creaming powder, soup stock cube, powdery cosmetics, and any other product which is hygroscopic or sells on its factory fresh flavor must be contained in a completely hermetic container so that it is prevented from being deteriorated by contacting with an ambient air or humidity before actually used by the user. For this purpose, the inner seal, which is sometimes referred to as "wadding tape" or "cap insert", has been practically and widely used to hermetically seal the container mouth.
An example of the inner seal comprises a reseal liner of a relatively thick cardboard and a relatively thin paper-coated aluminum foil membrane that is easily separably laminated onto the reseal liner. The reseal liner is fitted within a cap whereas the membrane is glued or heat-sealed onto the container mouth. When the cap is removed from the container mouth, the membrane separates from the reseal liner and remains onto the container mouth, which is then peeled off so that the product in the container becomes accessible to the user. Even after the membrane has been removed, in-use protection of the product may be obtained by re-capping the container because the reseal liner within the cap will substantially hermetically seal the container mouth.
In accordance with the typical conventional sealing technique using the above-described inner seal, glue is applied to the rim of the container mouth and the container is capped in such a manner that glassine paper coated on the underside of the aluminum foil is placed over the glued rim, followed by natural cooling. Such conventional sealing technique is disclosed in Japanese Patent Publication Nos. 57-48466, 3-23429, 7-37268 and Japanese Utility-Model Publication Nos. 58-36685, 63-137756, for example.
However, it takes a long time, say. approximately one day, until glue on the rim is cured so as to completely close the container mouth, which means less productivity. Another disadvantage of this technique is that glue applied on the container mouth rim tends to be forced out to the inward or outward of the rim when capping. This is not only unattractive in commercial value but also unhygienic. When the container contains powdery product such as house instant coffee and powdery cosmetics, it would be attracted to and contaminated by the uncured glue remaining within the mouth of the container.
Recent trend of the sealing technique is to laminate thermoplastic resin film as the lowermost layer of the membrane. After capping, the cap is heated to a temperature above a melting point of the thermoplastic resin to provide hermetical closure to the container mouth. Such technique is disclosed in Japanese Utility-Model Publication No. 50-32540, 7-2451, 7-2452, 7-2453, Japanese Utility-Model Un-examined Publication Nos. 52-147652, 4-32958, Japanese Patent Un-examined Publication No. 4-72156, for example. The heat-sealing process in this technique is completed in a shorter period. However, the membrane is excessively strongly heat-sealed to the container mouth and, therefore, not easy to be peeled off by the user. Moreover, after the membrane is removed, at least a portion of the cured glue is deposited on the rim surface of the container mouth, which appears uncleanly and degrades reseal property when the container is capped with the cap having the reseal liner.
The inner seal is usually supplied in a continuous reel form in pre-determined widths on cardboard cores. The thermoplastic resin film used in the above-described conventional one has substantially a flat surface, which tends to result in a "blocking" when reeled.